1. Field of the Invention
The present invention relates to a variable capacitor used for a high frequency circuit of a high frequency apparatus, and more particularly to a variable capacitor formed by a multilayer circuit board.
2. Description of the Related Art
In recent years, a high frequency apparatus including a variable capacitor has been increasingly miniaturized, and is employed in portable personal communications devices. Along with this, the use environment of the high frequency apparatus is becoming increasingly severe. For example, the high frequency apparatus is often subjected to vibrations during use, shocks from being dropped and temperature changes due to an abrupt change in the use environment.
A conventional variable capacitor will now be described. FIGS. 1A to 1C are views each showing a typical structure of the conventional variable capacitor. FIG. 1A is a plan view, FIG. 1B is a cross-sectional view and FIG. 1C is a partially plan view. In FIGS. 1A to 1C, there are shown an adjusting pin 11, a rotor electrode 12, a stator electrode 13, a rotor 14 and an area 15 of a portion where the rotor electrode 12 and the stator electrode 13 are overlapped together with a dielectric substance.
The operation of the conventional variable capacitor configured as described above will be now be described. Firstly, the rotor 14 is so constructed as to move rotationally together with the adjusting pin 11. Next, the adjusting pin 11 is rotated to move the rotor electrode 12 installed in the rotor 14 to the position where it overlaps the stator electrode 13 to some extent. The capacitance of the variable capacitor is determined by the size of the area 15 of a portion where the rotor electrode 12 and the stator electrode 13 are overlapped together with a dielectric substance.
Thus, even in the conventional variable capacitor, the capacitance can be varied by rotating the adjusting pin 11.
However, since variation of capacitance depends on a mechanical adjustment, the above conventional variable capacitor has a problem that many failures in the mechanical portions thereof are generated by adding thereto vibrations during use shocks when the apparatus is dropped and hot and cold temperature cycles due to a use environment.